Tantalum sputtering target

ABSTRACT

A tantalum sputtering target, wherein when the sum of the overall crystalline orientation is 1 on a tantalum target surface, the area ratio of crystals having any orientation among (100), (111), (110) does not exceed 0.5. Thus, obtained is a tantalum sputtering target having superior deposition properties where the deposition speed is high, film evenness (uniformity) is superior, and generation of arcings or particles is reduced.

TECHNICAL FIELD

The present invention relates to a tantalum sputtering target having arandom crystalline orientation, high deposition speed, superior filmevenness (uniformity), reduced generation of arcings or particles andfavorable target use efficiency.

BACKGROUND ART

In recent years, the sputtering method for forming a film from materialssuch as metal or ceramics has been used in numerous fields such aselectronics, corrosion resistant materials and ornaments, catalysts, aswell as in the manufacture of cutting/grinding materials and abrasionresistant materials.

Although the sputtering method itself is a well-known method in theforegoing fields, recently, particularly in the electronics field, atantalum sputtering target suitable for forming films of complex shapesand forming circuits is in demand.

Generally, this tantalum target is manufactured by forging and annealing(heat treatment) an ingot or billet formed by performing electron beammelting and casting to a tantalum material, and thereafter performingrolling and finish processing (mechanical processing, polishing, etc.)thereto.

In this kind of manufacturing procedure, the tantalum sputtering targetis manufactured in such a way that the cast structure of the ingot orbillet will destroy by the hot forging, disperse or eliminate the poresand segregations, and, by further annealing this, recrystallization willoccur, and the precision and strength of the structure can be improved.

Generally speaking, a molten and cast ingot or billet has a crystalgrain diameter of 50 mm or more. And, as a result of subjecting thisingot or billet to hot forging and recrystallization annealing, the caststructure will be destroyed, and a generally uniform and fine (100 μm orless) crystal grains can be obtained.

Meanwhile, when sputtering is performed with a target manufactured asdescribed above, it is said that the recrystallization structure of thetarget will become more fine and uniform, and uniform deposition willbecome possible with targets having a crystal orientation arranged in aspecific direction, and a film with reduced generation of arcings andparticles, and having stable properties can be obtained.

Thus, in the manufacturing process of the target, measures for makingthe recrystallization structure fine and uniform, and arranging thecrystal orientation in a specific direction are being adopted (e.g.,refer to Patent Documents 1 and 2).

When observing the mechanism of recrystallization, generally speaking, arecrystallized structure is an aggregate of individual crystals withrespectively different plane orientations, and each crystal is dividedby a grain boundary. Before rearrangement occurs, the strain added tothe object via plastic working such as cold rolling is absorbed in theprimary crystals by the transgranular slip in a certain direction, andthe strain is accumulated therein.

Such strained primary crystals take on a network cell structure that isextremely fine with slightly different orientations aggregated withlattice defects such as transition, and are also separated into aplurality of different areas with significantly differing orientations.When this kind of deformation structure is heated, the cells change intosubgrains (recovery process) through the combination of transition orrearrangement. The change from a cell into a subgrain hardly involvesany change in the measurement.

And, it is considered that these subgrains are combined, and a specificsubgrain grows to become a recrystallized core, corrodes thenon-recrystallized portion, grows and promotes the recrystallization.

With a tantalum target, it is said that a target having a fullyrecrystallized structure based on full annealing, and, as describedabove, having a specific crystal orientation is favorable in stabilizingthe structure.

When sputtering is performed with a tantalum target as described above,there are problems in that the evenness (uniformity) of the film willbecome inferior, the generation of arcings and particles will bepromoted, and the quality of sputtering deposition will deteriorate.[Patent Document 1] PCT(WO)2002-518593 [Patent Document 2] U.S. Pat. No.6,331,233

DISCLOSURE OF THE INVENTION

Thus, an object of the present invention is to obtain a tantalumsputtering target having superior deposition properties where thedeposition speed is high, film evenness (uniformity) is superior, andgeneration of arcings or particles is reduced in comparison to aconventional tantalum target with an arrangement with a specific crystalorientation.

In order to overcome the foregoing problems, the present inventorsdiscovered that a tantalum sputtering target having superior depositionproperties in comparison to conventional tantalum targets can beobtained by improving and devising the target structure and randomizingthe crystal orientation.

Based on the foregoing discovery, the present invention provides: 1) atantalum sputtering target, wherein when the sum of the overallcrystalline orientation is 1 on a tantalum target surface, the arearatio of crystals having any orientation among (100), (111) and (110)does not exceed 0.5; 2) a tantalum sputtering target, wherein when thesum of the overall crystalline orientation is 1 on a tantalum targetsurface, the sum of the area ratio of crystals having any twoorientations among (100), (111) and (110) does not exceed 0.75; 3) thetantalum sputtering target according to 1) above, wherein when the sumof the overall crystalline orientation is 1 on a tantalum targetsurface, the sum of the area ratio of crystals having any twoorientations among (100), (111) and (110) does not exceed 0.75; and 4)the tantalum sputtering target according to any one of 1) to 3) above,wherein the tantalum target surface is a sputtered erosion face.

The present invention also provides: 5) a tantalum sputtering target,wherein when the sum of the overall crystalline orientation is 1 on atantalum target surface, the area ratio of crystals having anyorientation among (100)<001>, (111)<001>and (110)<001>and in which therotation error is within 10° against an ND axis (orientation axis normalto rolling plane) does not exceed 0.5; 6) a tantalum sputtering target,wherein when the sum of the overall crystalline orientation is 1 on atantalum target surface, the sum of the area ratio of crystals havingany two orientations among (100)<001>, (111)<001>and (110)<001>and inwhich the rotation error is within 10° against an ND axis (orientationaxis normal to rolling plane) does not exceed 0.75; 7) the tantalumsputtering target according to 5) above, wherein when the sum of theoverall crystalline orientation is 1 on a tantalum target surface, thesum of the area ratio of crystals having any two orientations among(100)<001>, (111)<001>and (110)<001>and in which the rotation error iswithin 10° against an ND axis (orientation axis normal to rolling plane)does not exceed 0.75; and 8) the tantalum sputtering target according toany one of 5) to 7) above, wherein the tantalum target surface is asputtered erosion face.

The present invention also provides: 9) a tantalum sputtering target,wherein when the strength is measured with the complete randomness ofthe crystal orientation being 1 in a pole figure based on EBSP measuringthe (100) orientation on a tantalum target surface, a strength of 1 ormore is represented with a scale divided into 6 parts, and the θ in thepole figure has a peak having a strength of 1 or more not only in the 0°or 90° direction, but also in a direction therebetween; and 10) thetantalum sputtering target according to any one of 1) to 9) above,wherein when the strength is measured with the complete randomness ofthe crystal orientation being 1 in a pole figure based on EBSP measuringthe (100) orientation on a tantalum target surface, a strength of 1 ormore is represented with a scale divided into 6 parts, and the θ in thepole figure has a peak having a strength of 1 or more not only in the 0°or 90° direction, but also in a direction therebetween.

The present invention also provides: 11) a tantalum sputtering target,wherein when the strength is measured with the complete randomness ofthe crystal orientation being 1 in a pole figure based on EBSP measuringthe (100) orientation on a tantalum target surface, a strength of 1 ormore is represented with a scale divided into 6 parts, and the portionshown with a peak having a strength of 1 or more appearing outside theND direction (0°) in the pole figure has a spread of 20° or more; 12)the tantalum sputtering target according to any one of 1) to 9) above,wherein when the strength is measured with the complete randomness ofthe crystal orientation being 1 in a pole figure based on EBSP measuringthe (100) orientation on a tantalum target surface, a strength of 1 ormore is represented with a scale divided into 6 parts, and the portionshown with a peak having a strength of 1 or more appearing outside theND direction (0°) in the pole figure has a spread of 20° or more; 13)the [tantalum sputtering] target according to any one of 1) to 12)above, wherein the average crystal grain size of the target is 80 μm orless; 14) the [tantalum sputtering] target according to any one of 1) to13) above, wherein the target has a fine structure based on aroll-processed structure, and when the target surface is analyzed withEBSP, crystal grains having a crystal grain size of 25 to 150 μm existin an amount of 100 to 1000 crystal grains/mm²15) the tantalumsputtering target according to 14) above, wherein the tantalum targetsurface is a sputtered erosion face; and 16) the target according to anyone of 1) to 15) above, wherein the purity of the target is 99.99% ormore.

Effect of the Invention

The present invention yields a superior effect in that it is able toprovide a tantalum sputtering target having superior depositionproperties where the deposition speed is high, film evenness(uniformity) is superior, generation of arcings or particles is reducedand the use efficiency of the target is favorable in comparison to aconventional tantalum target with a crystal orientation arranged on thetarget surface.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a micrograph (magnification×100) showing the tantalum targetobtained by performing the cold finishing processing andrecrystallization annealing of the present invention.

FIG. 2 is a micrograph (magnification×50) showing the tantalum targetobtained by performing the cold finishing processing andrecrystallization annealing of the present invention.

FIG. 3 is a micrograph (magnification×100) showing the tantalum targetobtained by performing conventional forging and recrystallizationannealing.

FIG. 4 is a micrograph (magnification×50) showing the tantalum targetobtained by performing conventional forging and recrystallizationannealing.

BEST MODE FOR CARRYING OUT THE INVENTION

The sputtering target of the present invention having a random crystalorientation is generally manufactured with the following process.

To exemplify a specific example, foremost, a tantalum raw material(usually, high purity tantalum of 4N (99.99%) or more is used) is meltedvia electronic beam melting or the like, and this is cast to prepare aningot or billet. Next, this ingot or billet is subject to a series ofprocessing steps including annealing—forging, rolling, annealing (heattreatment), finish processing and so on.

Specifically, for instance, the foregoing ingot is subject to annealing(first time) at a temperature of 1373K to 1673K—cold forging (firsttime)—recrystallization annealing (second time) at a temperature betweenthe recrystallization starting temperature and 1373K—cold forging(second time)—recrystallization annealing (third time) at a temperaturebetween the recrystallization starting temperature and 1373K—cold (hot)rolling (first time)—recrystallization annealing at a temperaturebetween the recrystallization starting temperature and 1373K (fourthtime)—cold (hot) rolling (second time as required)—recrystallizationannealing at a temperature between the recrystallization startingtemperature and 1373K (fifth time as required)—finish processing to forma target material.

The forging or rolling performed to the ingot or billet will destroy thecast structure, disperse or eliminate the pores and segregations, and,by further annealing this, recrystallization will occur, and theprecision and strength of the structure can be improved to a certaindegree.

In the foregoing process, although the recrystallization annealing maybe performed only once, by repeating this twice, the structural defectscan be effectively reduced. Further, cold (hot) rolling andrecrystallization annealing at a temperature between therecrystallization starting temperature and 1373K may be repeated or maybe performed for one cycle. Thereafter, this is ultimately finished in atarget shape via finish processing such as machining or polishing.

Although the tantalum target is manufactured with the foregoingmanufacturing process, what is particularly important in the presentinvention is that the crystal orientation is made random as possiblewithout arranging such crystal orientation of the target in a specificdirection. Therefore, although a preferable example of the manufacturingprocess was described above, the present invention is not limited to theforegoing manufacturing process so as long as the manufacturing processis able to achieve the random crystal orientation of the presentinvention.

During the series of processes, it is necessary to destroy the caststructure with forging and rolling, and to sufficiently performrecrystallization. In the present invention also, after performing theprocesses of forging and rolling to the molten and cast tantalum ingotor billet, it is desirable to perform recrystallization annealing at atemperature between the recrystallization starting temperature and 1673Kso as to make the structure fine and uniform. In other words, prior tothe final process, the improvement of material characteristics is soughtby making the structure fine and uniform pursuant to therecrystallization similar to conventional methods.

In the present invention, it is desirable to perform annealing at atemperature of 1273K or less after the final plastic working processsuch as rolling. When performing such annealing, there is an effect ofalleviating the warping or deformation of the target. This is thereaftersubject to finish processing (machining or the like) so as to form atarget shape.

The structure of the tantalum target obtained thereby will have arecrystallization structure based on a roll-processed structure, and thecrystal orientation will become random. In other words, obtained is atantalum sputtering target, wherein, when the sum of the overallcrystalline orientation is 1 on a tantalum target surface, the arearatio of crystals having any orientation among (100), (111) and (110)will not exceed 0.5. When the area ratio exceeds 0.5, a specific crystalorientation will become preferential, and the object of the presentinvention cannot be achieved.

Further, with the present invention, when the sum of the overallcrystalline orientation is 1 on a tantalum target surface, it isdesirable that the sum of the area ratio of crystals having any twoorientations among (100), (111) and (110) does not exceed 0.75. This isalso a favorable condition for randomizing the crystal orientation.

With this kind of tantalum target surface, it is desirable that thesputtered erosion face, in addition to the face prior to being subjectto sputtering, comprises the foregoing condition of a random crystalorientation, and this is required in order to sufficiently achieve theobject and effect of the present invention.

The present invention is desirably a tantalum sputtering target,wherein, when the sum of the overall crystalline orientation is 1 on atantalum target surface, the area ratio of crystals having anyorientation among (100)<001>, (111)<001> and (110)<001> and in which therotation error is within 10° against an ND directional axis (rolled facenormal directional axis) does not exceed 0.5.

Similarly, the present invention is also desirably a tantalum sputteringtarget, wherein when the sum of the overall crystalline orientation is 1on a tantalum target surface, the sum of the area ratio of crystalshaving any two orientations among (100)<001>, (111)<001> and (110)<001>and in which the rotation error is within 10° against an ND axis(orientation axis normal to rolling plane) does not exceed 0.75.

A tantalum sputtering target, wherein when the sum of the overallcrystalline orientation is 1 on a tantalum target surface, the sum ofthe area ratio of a crystal having any two orientations among(100)<001>, (111)<001> and (110)<001> and in which the rotation error iswithin 10° against an ND axis (orientation axis normal to rolling plane)does not exceed 0.75, and the tantalum target surface being a sputterederosion face are also desirable conditions for achieving the object andeffect of the present invention of randomizing the crystal orientationof the target.

The present invention is also desirably a tantalum sputtering target,wherein when the strength is measured with the complete randomness ofthe crystal orientation being 1 in a pole figure based on EBSP measuringthe (100) orientation on a tantalum target surface, a strength of 1 ormore is represented with a scale divided into 6 parts, and the θ in thepole figure has a peak having a strength of 1 or more not only in the 0°or 90° direction, but also in a direction therebetween. As a result, therandom orientation can be further controlled.

As further desirable conditions of the present invention, the averagecrystal grain size of the target is 80 μm or less, and the target has afine structure based on a roll-processed structure; when the targetsurface is analyzed with EBSP, crystal grains having a crystal grainsize of 25 to 150 μm exist in an amount of 100 to 1000 crystalgrains/mm²; and the purity of the target is 99.99% or more. Theconditions of making the crystal grains smaller and randomizing thecrystal orientation will yield the effect of improving the uniformity ofsputtering.

The structure of the tantalum target according to the present invention(annealed at 1173K) is shown in FIG. 1 (magnification×100) and FIG. 2(magnification×50).

Further, a conventional recrystallized structure (subject torecrystallization annealing at 1373K) is shown in FIG. 3(magnification×100) and FIG. 4 (magnification×50). As shown in thedrawings, the structure of the tantalum target according to the presentinvention is clearly different from the conventional recrystallizedstructure.

Further, a target finished with plastic working such as rolling withoutbeing subject to annealing generates strain due to the heat from thesputtering operation depending on the processing conditions, and warping(bending) or cracks may occur. In the present invention, however, suchstrain will not be generated.

Moreover, this target material will have a Vickers hardness of 90 ormore, Vickers hardness of 100 or more, or Vickers hardness of 125 ormore, and a target superior in strength can be obtained.

What is most important in the present invention is to aim for a morerandom crystal orientation via rolling and recrystallization annealing,and to provide such random crystal orientation of the present inventionnot only to the target surface, but also to the erosion face appearingin the sputtered face at the stage where erosion is progressing.

This kind of target structure has a significant effect in improving theuniformity. Since this kind of structure can be realized merely bychanging the final heat treatment process, it is applicable to anyimproved versions heretofore and there will be no increase of costs.

The present invention is now explained in detail with reference to theExamples. These Examples are merely illustrative, and the presentinvention shall in no way be limited thereby. In other words, thepresent invention shall only be limited by the scope of claim for apatent, and shall include the various modifications other than theExamples of this invention.

EXAMPLE 1

A tantalum raw material having a purity of 99.997% was subject toelectron beam melting, and this was cast to prepare an ingot or billethaving a thickness of 200 mm and diameter of 200 mm φ. The crystal graindiameter in this case was approximately 55 mm.

Next, after performing extend forging to this ingot or billet at roomtemperature, this was subject to recrystallization annealing at atemperature of 1500K. As a result, a material having a structure inwhich the average crystal grain diameter is 200 μm, thickness of 100 mm,and diameter of 100 mm φ was obtained.

Next, this was subject to extend forging and upset forging at roomtemperature once again, and recrystallization annealing was performedthereto again at a temperature of 1480K. As a result, a material havinga structure in which the average crystal grain diameter is 100 μm,thickness of 100 mm, and diameter of 100 mm φ was obtained.

Next, this was subject to cold extend forging and upset forging, andrecrystallization annealing at 1173K, subsequently subject to coldrolling once again, and annealing at 1173K (900° C.) thereafter as wellas finish processing, so as to obtain a target material having athickness of 10 mm and diameter of 320 mm φ.

As a result of performing the foregoing process, it was possible toobtain a tantalum sputtering target having a random orientation wherein,when the sum of the overall crystalline orientation is 1 on a tantalumtarget surface, the areas ratio of orientations of (100), (111) and(110) are 0.5, 0.4 and 0.1, respectively. Further, this target had astructure where the sputtered erosion face described later also had asimilar orientation.

The average crystal grain size of the target was 40 μm, and, when thetarget surface was analyzed with EBSP, crystal grains having a crystalgrain size of 30 to 100 μm existed in an amount of 100 to 1000 crystalgrains/mm².

Incidentally, since the sheet resistance depends on the film thickness,distribution of the sheet resistance within the wafer (8 inch) wasmeasured, and the status of film thickness distribution was examinedthereby.

Specifically, the sheet resistance at 49 points on the wafer wasmeasured, and the standard deviation (σ) was calculated. The results areshown in Table 1.

As evident from Table 1, in Example 1, variation in the resistancedistribution within the sheet from the initial stage of sputtering tothe final stage of sputtering was small (2.6 to 3.2%); that is,variation in the film thickness distribution was small.

As described above, the tantalum target of Example 1 has a highdeposition speed, favorable film uniformity, little variation in thefilm thickness with an 8-inch wafer, and no generation of arcings orparticles, and was therefore capable of improving the quality ofsputtering deposition. TABLE 1 Transition of Film Thickness Distributionin Wafer Comparative Comparative Comparative Example 1 Example 2 Example3 Example 4 Example 5 Example 6 Example 1 Example 2 Example 3 InitialStage of Sputtering 2.60% 3.10% 3.10% 2.80% 3.00% 2.50% 4.50% 5.00%3.90% Middle Stage of Sputtering 2.80% 3.10% 3.20% 3.00% 3.10% 3.20%5.50% 4.70% 4.50% Final Stage of Sputtering 3.20% 3.30% 3.40% 3.20%3.30% 3.30% 5.50% 5.30% 4.50%

EXAMPLE 2

A tantalum raw material having a purity of 99.997% was subject toelectron beam melting, and this was cast to prepare an ingot or billethaving a thickness of 200 mm and diameter of 200 mm φ. The crystal graindiameter in this case was approximately 50 mm.

Next, after performing extend forging to this ingot or billet at roomtemperature, this was subject to recrystallization annealing at atemperature of 1500K. As a result, a material having a structure inwhich the average crystal grain diameter is 200 μm, thickness of 100 mm,and diameter of 100 mm φ was obtained.

Next, this was subject to extend forging and upset forging at roomtemperature once again, and recrystallization annealing was performedthereto again at a temperature of 1173K. As a result, a material havinga structure in which the average crystal grain diameter is 80 μm,thickness of 100 mm, and diameter of 100 mm φ was obtained.

Next, this was subject to cold extend forging and upset forging, andrecrystallization annealing at 1173K, subsequently subject to coldrolling once again, annealing at 1173K (900° C.) twice as well as finishprocessing, so as to obtain a target material having a thickness of 10mm and diameter of 320 mm φ.

As a result of performing the foregoing process, it was possible toobtain a tantalum sputtering target having a random orientation wherein,when the sum of the overall crystalline orientation is 1 on a tantalumtarget surface, the areas ratio of orientations of (100), (111) and(110) are 0.4, 0.4 and 0.1, respectively. Further, this target had astructure where the sputtered erosion face described later also had asimilar orientation.

The average crystal grain size of the target was 60 μm, and, when thetarget surface was analyzed with EBSP, crystal grains having a crystalgrain size of 40 to 120 μm existed in an amount of 100 to 1000 crystalgrains/mm².

Incidentally, since the sheet resistance depends on the film thickness,distribution of the sheet resistance within the wafer (8 inch) wasmeasured, and the status of film thickness distribution was examinedthereby.

Specifically, the sheet resistance at 49 points on the wafer wasmeasured, and the standard deviation (σ) was calculated. The results areshown in Table 1.

As evident from Table 1, in Example 2, variation in the resistancedistribution within the sheet from the initial stage of sputtering tothe final stage of sputtering was small (3.1 to 3.3%); that is,variation in the film thickness distribution was small.

As described above, the tantalum target of Example 2 has a highdeposition speed, favorable film uniformity, little variation in thefilm thickness with an 8-inch wafer, and no generation of arcings orparticles, and was therefore capable of improving the quality ofsputtering deposition.

EXAMPLE 3

A tantalum raw material having a purity of 99.997% was subject toelectron beam melting, and this was cast to prepare an ingot or billethaving a thickness of 200 mm and diameter of 200 mm φ. The crystal graindiameter in this case was approximately 60 mm.

Next, after performing extend forging to this ingot or billet at roomtemperature, this was subject to recrystallization annealing at atemperature of 1500K. As a result, a material having a structure inwhich the average crystal grain diameter is 200 μm, thickness of 100 mm,and diameter of 100 mm φ was obtained.

Next, this was subject to extend forging and upset forging at roomtemperature once again, and recrystallization annealing was performedthereto again at a temperature of 1173K. As a result, a material havinga structure in which the average crystal grain diameter is 80 μm,thickness of 100 mm, and diameter of 100 mm φ was obtained.

Next, this was subject to cold extend forging and upset forging, andrecrystallization annealing at 1173K, subsequently subject to coldrolling once again, annealing at 1173K (900° C.), cold rolling,annealing at 1273K (1000° C.) as well as finish processing, so as toobtain a target material having a thickness of 10 mm and diameter of 320mm φ.

As a result of performing the foregoing process, it was possible toobtain a tantalum sputtering target having a random orientation wherein,when the sum of the overall crystalline orientation is 1 on a tantalumtarget surface, the areas ratio of orientations of (100), (111) and(110) are 0.3, 0.4 and 0.1, respectively. Further, this target had astructure where the sputtered erosion face described later also had asimilar orientation.

The average crystal grain size of the target was 80 μm, and, when thetarget surface was analyzed with EBSP, crystal grains having a crystalgrain size of 50 to 150 μm existed in an amount of 100 to 1000 crystalgrains/mm².

Incidentally, since the sheet resistance depends on the film thickness,distribution of the sheet resistance within the wafer (8 inch) wasmeasured, and the status of film thickness distribution was examinedthereby.

Specifically, the sheet resistance at 49 points on the wafer wasmeasured, and the standard deviation (σ) was calculated. The results areshown in Table 1.

As evident from Table 1, in Example 3, variation in the resistancedistribution within the sheet from the initial stage of sputtering tothe final stage of sputtering was small (3.1 to 3.4%); that is,variation in the film thickness distribution was small.

As described above, the tantalum target of Example 3 has a highdeposition speed, favorable film uniformity, little variation in thefilm thickness with an 8-inch wafer, and no generation of arcings orparticles, and was therefore capable of improving the quality ofsputtering deposition.

EXAMPLE 4

A tantalum raw material having a purity of 99.997% was subject toelectron beam melting, and this was cast to prepare an ingot or billethaving a thickness of 200 mm and diameter of 200 mm φ. The crystal graindiameter in this case was approximately 55 mm.

Next, after performing extend forging to this ingot or billet at roomtemperature, this was subject to recrystallization annealing at atemperature of 1500K. As a result, a material having a structure inwhich the average crystal grain diameter is 200 μm, thickness of 100 mm,and diameter of 100 mm φ was obtained.

Next, this was subject to extend forging and upset forging at roomtemperature once again, and recrystallization annealing was performedthereto again at a temperature of 1480K. As a result, a material havinga structure in which the average crystal grain diameter is 100 μm,thickness of 100 mm, and diameter of 100 mm φ was obtained.

Next, this was subject to cold extend forging and upset forging, andrecrystallization annealing at 1173K, subsequently subject to coldrolling once again, and annealing at 1173K (900° C.) thereafter as wellas finish processing, so as to obtain a target material having athickness of 10 mm and diameter of 320 mm φ.

As a result of performing the foregoing process, it was possible toobtain a tantalum sputtering target having a random orientation wherein,when the sum of the overall crystalline orientation is 1 on a tantalumtarget surface, the ratio areas of a crystal having the orientations of(100)<001>, (111)<001> and (110)<001>, and in which the rotation erroris within 10° against an ND axis (orientation axis normal to rollingplane)are 0.3, 0.3 and 0.1, respectively. Further, this target had astructure where the sputtered erosion face described later also had asimilar orientation.

The average crystal grain size of the target was 35 μm, and, when thetarget surface was analyzed with EBSP, crystal grains having a crystalgrain size of 30 to 100 μm existed in an amount of 100 to 1000 crystalgrains/mm².

Incidentally, since the sheet resistance depends on the film thickness,distribution of the sheet resistance within the wafer (8 inch) wasmeasured, and the status of film thickness distribution was examinedthereby.

Specifically, the sheet resistance at 49 points on the wafer wasmeasured, and the standard deviation (σ) was calculated. The results areshown in Table 1.

As evident from Table 1, in Example 4, variation in the resistancedistribution within the sheet from the initial stage of sputtering tothe final stage of sputtering was small (2.8 to 3.2%); that is,variation in the film thickness distribution was small.

As described above, the tantalum target of Example 4 has a highdeposition speed, favorable film uniformity, little variation in thefilm thickness with an 8-inch wafer, and no generation of arcings orparticles, and was therefore capable of improving the quality ofsputtering deposition.

EXAMPLE 5

A tantalum raw material having a purity of 99.997% was subject toelectron beam melting, and this was cast to prepare an ingot or billethaving a thickness of 200 mm and diameter of 200 mm φ. The crystal graindiameter in this case was approximately 55 mm.

Next, after performing extend forging to this ingot or billet at roomtemperature, this was subject to recrystallization annealing at atemperature of 1500K. As a result, a material having a structure inwhich the average crystal grain diameter is 200 μm, thickness of 100 mm,and diameter of 100 mm φ was obtained.

Next, this was subject to extend forging and upset forging at roomtemperature once again, and recrystallization annealing was performedthereto again at a temperature of 1173K. As a result, a material havinga structure in which the average crystal grain diameter is 80 μm,thickness of 100 mm, and diameter of 100 mm φ was obtained.

Next, this was subject to cold extend forging and upset forging, andrecrystallization annealing at 1173K, subsequently subject to coldrolling and annealing at 1173K (900° C.) that were performed twice, andfinish processing was performed so as to obtain a target material havinga thickness of 10 mm and diameter of 320 mm φ.

As a result of performing the foregoing process, it was possible toobtain a tantalum sputtering target having a random orientation wherein,when the sum of the overall crystalline orientation is 1 on a tantalumtarget surface, the area ratio of crystals having the orientations of(100)<001>, (111)<001>, (110)<001>, and in which the rotation error iswithin 10° against an ND axis (orientation axis normal to rollingplane)are 0.5, 0.2 and 0.1, respectively. Further, this target had astructure where the sputtered erosion face described later also had asimilar orientation.

The average crystal grain size of the target was 60 μm, and, when thetarget surface was analyzed with EBSP, crystal grains having a crystalgrain size of 40 to 120 μm existed in an amount of 100 to 1000 crystalgrains/mm².

Incidentally, since the sheet resistance depends on the film thickness,distribution of the sheet resistance within the wafer (8 inch) wasmeasured, and the status of film thickness distribution was examinedthereby.

Specifically, the sheet resistance at 49 points on the wafer wasmeasured, and the standard deviation (σ) was calculated. The results areshown in Table 1.

As evident from Table 1, in Example 5, variation in the resistancedistribution within the sheet from the initial stage of sputtering tothe final stage of sputtering was small (3.0 to 3.3%); that is,variation in the film thickness distribution was small.

As described above, the tantalum target of Example 5 has a highdeposition speed, favorable film uniformity, little variation in thefilm thickness with an 8-inch wafer, and no generation of arcings orparticles, and was therefore capable of improving the quality ofsputtering deposition.

EXAMPLE 6

A tantalum raw material having a purity of 99.997% was subject toelectron beam melting, and this was cast to prepare an ingot or billethaving a thickness of 200 mm and diameter of 200 mm φ. The crystal graindiameter in this case was approximately 50 mm.

Next, after performing extend forging to this ingot or billet at roomtemperature, this was subject to recrystallization annealing at atemperature of 1500K. As a result, a material having a structure inwhich the average crystal grain diameter is 200 μm, thickness of 100 mm,and diameter of 100 mm φ was obtained.

Next, this was subject to extend forging and upset forging at roomtemperature once again, and recrystallization annealing was performedthereto again at a temperature of 1173K. As a result, a material havinga structure in which the average crystal grain diameter is 80 μm,thickness of 100 mm, and diameter of 100 mm φ was obtained.

Next, this was subject to cold extend forging and upset forging, andrecrystallization annealing at 1173K, subsequently subject to coldrolling once again, annealing at 1173K (900° C.), cold rolling,annealing at 1273K (1000° C.) as well as finish processing, so as toobtain a target material having a thickness of 1 mm and diameter of 320mm φ.

As a result of performing the foregoing process, it was possible toobtain a tantalum sputtering target having a random orientation wherein,when the sum of the overall crystalline orientation is 1 on a tantalumtarget surface, the area ratio of crystals having the orientations of(100)<001>, (111)<001>, (110)<001>, and in which the rotation error iswithin 10° against an ND axis (orientation axis normal to rollingplane)are 0.2, 0.4 and 0.1, respectively. Further, this target had astructure where the sputtered erosion face described later also had asimilar orientation.

The average crystal grain size of the target was 80 μm, and, when thetarget surface was analyzed with EBSP, crystal grains having a crystalgrain size of 50 to 150 μm existed in an amount of 100 to 1000 crystalgrains/mm².

Incidentally, since the sheet resistance depends on the film thickness,distribution of the sheet resistance within the wafer (8 inch) wasmeasured, and the status of film thickness distribution was examinedthereby.

Specifically, the sheet resistance at 49 points on the wafer wasmeasured, and the standard deviation (σ) was calculated. The results areshown in Table 1.

As evident from Table 1, in Example 6, variation in the resistancedistribution within the sheet from the initial stage of sputtering tothe final stage of sputtering was small (2.5 to 3.3%); that is,variation in the film thickness distribution was small.

As described above, the tantalum target of Example 6 has a highdeposition speed, favorable film uniformity, little variation in thefilm thickness with an 8-inch wafer,. and no generation of arcings orparticles, and was therefore capable of improving the quality ofsputtering deposition.

COMPARATIVE EXAMPLE 1

As with Example 1, a tantalum raw material having a purity of 99.997%was subject to electron beam melting, and this was cast to prepare aningot or billet having a thickness of 200 mm and diameter of 200 mm φ.The crystal grain diameter in this case was approximately 55 mm. Next,after performing extend forging and upset forging to this ingot orbillet at room temperature, this was subject to recrystallizationannealing at a temperature of 1173K. As a result, a material having astructure in which the average crystal grain diameter is 180 μm,thickness of 100 mm, and diameter of 100 mm φ was obtained.

Next, this was subject to extend forging and upset forging at roomtemperature once again, and recrystallization annealing was performedthereto again at a temperature of 1173K. As a result, a material havinga structure in which the average crystal grain diameter is 80 μm,thickness of 100 mm, and diameter of 100 mm φ was obtained.

Next, this was subject to cold rolling and recrystallization annealingat 1173K, as well as finish processing, so as to obtain a targetmaterial having a thickness of 10 mm and diameter of 320 mm φ.

The tantalum target obtained with the foregoing process had an averagecrystal grain size of 55 μm, and there were variations in certainlocations. It was possible to obtain a tantalum sputtering target havinga uniform orientation wherein, when the sum of the overall crystallineorientation is 1 on a tantalum target surface, the areas ratio oforientations of (100), (111) and (110) are 0.8, 0.2 and 0, respectively.

When performing sputtering with this tantalum target, evenness(uniformity) of the film was inferior, and caused the quality of sputterdeposition to deteriorate. The results are similarly shown in Table 1.

The results shown in Comparative Example 1 of Table 1 were obtained bymeasuring the sheet resistance at 49 points on the wafer (8 inch) aswith Example 1, and calculating the standard deviation (σ) thereof. InComparative Example 1, variation in the resistance distribution withinthe sheet from the initial stage of sputtering to the final stage ofsputtering was large (4.5 to 5.5%); that is, variation in the filmthickness distribution was significant.

Further, variation in the film thickness in an 8-inch wafer wassignificant, arcings and particles were generated, and this caused thequality of the sputtering deposition to deteriorate.

COMPARATIVE EXAMPLE 2

As with Example 1, a tantalum raw material having a purity of 99.997%was subject to electron beam melting, and this was cast to prepare aningot or billet having a thickness of 200 mm and diameter of 200 mm φ.The crystal grain diameter in this case was approximately 55 mm. Next,after performing cold mix forging to this ingot or billet at roomtemperature, this was subject to recrystallization annealing at atemperature of 1173K. As a result, a material having a structure inwhich the average crystal grain diameter is 180 μm, thickness of 100 mm,and diameter of 100 mm φ was obtained.

Next, this was subject to extend forging and upset forging at roomtemperature once again, and recrystallization annealing was performedthereto again at a temperature of 1173K. As a result, a material havinga structure in which the average crystal grain diameter is 80 μm,thickness of 100 mm, and diameter of 100 mm φ was obtained.

Next, this was subject to cold rolling and recrystallization annealingat 1373K, as well as finish processing, so as to obtain a targetmaterial having a thickness of 10 mm and diameter of 320 mm φ.

The tantalum target obtained with the foregoing process had coarsenedcrystals.

The tantalum target obtained with the foregoing process had an averagecrystal grain size of 96 μm, and there were variations. It was possibleto obtain a tantalum sputtering target having a uniform orientationwherein, when the sum of the overall crystalline orientation is 1 on atantalum target surface, the areas ratio of orientations of (100), (111)and (110) are 0.2, 0.7 and 0.1, respectively.

When performing sputtering with this tantalum target, evenness(uniformity) of the film was inferior, and caused the quality of sputterdeposition to deteriorate. The results are similarly shown in Table 1.

The results shown in Comparative Example 2 of Table 1 were obtained bymeasuring the sheet resistance at 49 points on the wafer (8 inch) aswith Example 1, and calculating the standard deviation (σ) thereof. InComparative Example 2, variation in the resistance distribution withinthe sheet from the initial stage of sputtering to the final stage ofsputtering was large (4.7 to 5.3%); that is, variation in the filmthickness distribution was significant.

Further, with this tantalum target, evenness (uniformity) of the filmwas inferior, variation in the film thickness in an 8-inch wafer wassignificant, arcings and particles were generated, and this caused thequality of the sputtering deposition to deteriorate.

COMPARATIVE EXAMPLE 3

As with Example 1, a tantalum raw material having a purity of 99.997%was subject to electron beam melting, and this was cast to prepare aningot or billet having a thickness of 200 mm and diameter of 200 mm φ.The crystal grain diameter in this case was approximately 55 mm. Next,after performing cold mix forging to this ingot or billet at roomtemperature, this was subject to recrystallization annealing at atemperature of 1173K. As a result, a material having a structure inwhich the average crystal grain diameter is 180 μm, thickness of 100 mm,and diameter of 100 mm φ was obtained.

Next, this was subject to extend forging and upset forging at roomtemperature once again, and recrystallization annealing was performedthereto again at a temperature of 1173K. As a result, a material havinga structure in which the average crystal grain diameter is 80 μm,thickness of 100 mm, and diameter of 100 mm φ was obtained.

Next, this was subject to cold rolling and recrystallization annealingat 1123K, as well as finish processing, so as to obtain a targetmaterial having a thickness of 10 mm and diameter of 320 mm φ.

The tantalum target obtained with the foregoing process had an averagecrystal grain size of 37 μm, and there were variations. It was possibleto obtain a tantalum sputtering target having a uniform orientationwherein, when the sum of the overall crystalline orientation is 1 on atantalum target surface, the area ratio of crystals having theorientations of (100)<001>, (111)<001>, (110)<001>, and in which therotation error is within 10° against an ND axis (orientation axis normalto rolling plane)are 0.7, 0.2 and 0.1, respectively. This tantalumtarget had a generally aligned orientation from the target surfacetoward the center part thereof.

When performing sputtering with this tantalum target, evenness(uniformity) of the film was inferior, and caused the quality of sputterdeposition to deteriorate. The results are similarly shown in Table 1.

The results shown in Comparative Example 3 of Table 1 were obtained bymeasuring the sheet resistance at 49 points on the wafer (8 inch) aswith Example 1, and calculating the standard deviation (σ) thereof. InComparative Example 3, variation in the resistance distribution withinthe sheet from the initial stage of sputtering to the final stage ofsputtering was large (3.9 to 4.5%); that is, variation in the filmthickness distribution was significant.

Further, with this tantalum target, evenness (uniformity) of the filmwas inferior, variation in the film thickness in an 8-inch wafer wassignificant, arcings and particles were generated, and this caused thequality of the sputtering deposition to deteriorate.

INDUSTRIAL APPLICABILITY

The present invention is not a target where the coarse crystals orcrystal orientation according to conventional recrystallizationannealing are arranged in a specific orientation, but is a tantalumtarget having a random orientation, and, therefore, this can be appliedto a tantalum sputtering target being demanded to be a high depositionspeed, superior film evenness (uniformity), reduced generation ofarcings or particles and favorable target use efficiency.

1. A tantalum sputtering target, wherein, when a sum of an overallcrystalline orientation of a surface of said tantalum sputtering targetis 1, an area ratio of crystals having any orientation among (100),(111) and (110) does not exceed 0.5.
 2. A tantalum sputtering target,wherein, when a sum of an overall crystalline orientation of a surfaceof said tantalum sputtering target is 1, a sum of an area ratio ofcrystals having any two orientations among (100), (111) and (110) doesnot exceed 0.75.
 3. The tantalum sputtering target according to claim 1,wherein when the sum of the overall crystalline orientation of saidsurface of said tantalum sputtering target is 1, a sum of the area ratioof crystals having any two orientations among (100), (111) and (110)does not exceed 0.75.
 4. (canceled)
 5. A tantalum sputtering target,wherein, when a sum of an overall crystalline orientation of a surfaceof said tantalum sputtering target is 1, an area ratio of crystalshaving any orientation among (100)<001>, (111)<001> and (110)<001> andin which a rotation error is within 10° against an ND axis (orientationaxis is normal to rolling plane) does not exceed 0.5.
 6. A tantalumsputtering target, wherein, when a sum of an overall crystallineorientation of a surface of said tantalum sputtering target is 1, a sumof the area ratio of crystals having any two orientations among(100)<001>, (111)<001> and (110)<001> and in which a rotation error iswithin 10° against an ND axis (orientation axis is normal to rollingplane) does not exceed 0.75.
 7. A tantalum sputtering target accordingto claim 5, wherein, when the sum of the overall crystalline orientationis 1 on said surface, the sum of the area ratio of crystals having anytwo orientations among (100)<001>, (111)<001> and (110)<001> and inwhich the rotation error is within 10° against an ND axis (orientationaxis is normal to rolling plane) does not exceed 0.75.
 8. (canceled) 9.A tantalum sputtering target, wherein, when a strength of said tantalumsputtering target is measured with complete randomness of crystalorientation being 1 in a pole figure based on EBSP measuring a (100)orientation on a surface of said tantalum sputtering target, a strengthof 1 or more is represented with a scale divided into 6 parts, and a θin the pole figure has a peak having a strength of 1 or more not only ina 0° or 90° direction, but also in a direction therebetween. 10.(canceled)
 11. A tantalum sputtering target, wherein, when a strength ismeasured with complete randomness of crystal orientation being 1 in apole figure based on EBSP measuring a (100) orientation on a surface ofsaid tantalum target, a strength of 1 or more is represented with ascale divided into 6 parts, and a portion shown with a peak having astrength of 1 or more appearing outside a ND direction (0°) in the polefigure has a spread of 20° or more. 12-14. (canceled)
 15. The tantalumsputtering target according to claim 25, wherein said surface is asputtered erosion face of said tantalum sputtering target. 16.(canceled)
 17. A tantalum sputtering target according to claim 3,wherein said surface is a sputtered erosion face of said tantalumsputtering target.
 18. A tantalum sputtering target according to claim17, wherein an average crystal grain size of said tantalum sputteringtarget is 80 μm or less.
 19. A tantalum sputtering target according toclaim 18, wherein said tantalum sputtering target has a fineroll-processed structure, and wherein, when said tantalum sputteringtarget is analyzed with EBSP, crystal grains having a crystal grain sizeof 25 to 150 μm exist in an amount of 100 to 1000 crystal grains/mm².20. A tantalum sputtering target according to claim 19, wherein a purityof said tantalum sputtering target is 99.99% or more.
 21. A tantalumsputtering target according to claim 1, wherein said surface is asputtered erosion face of said tantalum sputtering target.
 22. Atantalum sputtering target according to claim 1, wherein, when astrength of said tantalum sputtering target is measured with completerandomness of crystal orientation being 1 in a pole figure based on EBSPmeasuring a (100) orientation on a said surface of said tantalumsputtering target, a strength of 1 or more is represented with a scaledivided into 6 parts, and a θ in the pole figure has a peak having astrength of 1 or more not only in a 0° or 90° direction, but also in adirection therebetween.
 23. A tantalum sputtering target according toclaim 1, wherein, when a strength is measured with complete randomnessof crystal orientation being 1 in a pole figure based on EBSP measuringa (100) orientation on said surface of said tantalum sputtering target,a strength of 1 or more is represented with a scale divided into 6parts, and a portion shown with a peak having a strength of 1 or moreappearing outside a ND direction (0°) in the pole figure has a spread of20° or more.
 24. A tantalum sputtering target according to claim 1,wherein an average crystal grain size of said tantalum sputtering targetis 80 μm or less.
 25. A tantalum sputtering target according to claim 1,wherein said tantalum sputtering target has a fine roll-processedstructure, and wherein, when said tantalum sputtering target is analyzedwith EBSP, crystal grains having a crystal grain size of 25 to 150 μmexist in an amount of 100 to 1000 crystal grains/mm².
 26. A tantalumsputtering target according to claim 1, wherein a purity of saidtantalum sputtering target is 99.99% or more.
 27. A tantalum sputteringtarget according to claim 5, wherein said surface is a sputtered erosionface of said tantalum sputtering target.